1. Field of the Invention
The present invention relates to an ink-ejecting device and method of manufacture.
2. Description of Related Art
Non-impact-type printing devices have recently replaced conventional impact-type printing devices and have greatly propagated in the market. Ink-ejecting-type printing devices are known for simple operation and effective use in multi-gradation and coloration printing. Of these devices, drop-on-demand-type devices, which eject only ink droplets for printing, have propagated rapidly because of their excellent ejection efficiency and low operation cost.
A drop-on-demand device is disclosed in U.S. Pat. No. 3,946,398 to Kyser. A thermal-ejecting-type drop-on-demand device is disclosed in U.S. Pat. No. 4,723,129 to Endo. The former type is difficult to design in a compact size. The latter type requires ink having heat-resistance, because the ink is heated at high temperature. Accordingly, these devices are cumbersome to use and have many problems.
A shear-mode-type device, disclosed in U.S. Pat. No. 4,879,568 to Bartky et al., has been proposed to simultaneously solve the above problems.
As shown in FIGS. 9A and 9B, a shear-mode-type ink-ejecting device 600 as described above comprises a bottom wall 601, a ceiling wall 602 and a shear mode actuator wall 603 therebetween. The actuator wall 603 comprises a lower wall 607 that is adhesively attached to the bottom wall 601 and polarized in a direction as indicated by an arrow 611, and an upper wall 605 that is adhesively attached to the ceiling wall 602 and polarized in a direction as indicated by an arrow 609. A pair of actuator walls 603 thus formed forms an ink channel 613 therebetween, and a space 615 that is narrower than the ink channel 613 is formed between neighboring pairs of actuator walls 603.
A nozzle plate 617 having nozzles 618 formed therein is fixedly secured to one end of each ink channel 613, and electrodes 619 and 621 are provided as metallized layers on both side surfaces of each actuator wall 603. Each of the electrodes 619 and 621 is covered by an insulating layer (not shown) to insulate it from the ink. The electrodes 619, 621 that face the surface 615 are connected to the ground 623, and the electrodes that are provided in the ink channel 613 are connected to a silicon chip 625, which forms an actuator driving circuit.
Next, a manufacturing method for the ink-ejecting device 600 as described above will be described. First, a piezoelectric ceramic layer that is polarized in a direction as indicated by an arrow 611 is adhesively attached to the bottom wall 601, and a piezoelectric ceramic layer that is polarized in a direction as indicated by an arrow 609 is adhesively attached to the ceiling wall 602. The thickness of each piezoelectric ceramic layer is equal to the height of each of the lower wall 607 and the upper wall 605. Subsequently, parallel grooves are formed on the piezoelectric ceramic layers by rotating a diamond cutting disc or the like to form the lower wall 607 and the upper wall 605. Further, the electrode 619 is formed on the side surface of the lower wall 607 by a vacuum-deposition method, and the insulating layer as described above is provided onto the electrode 619. Likewise, the electrode 621 is provided on the side surface of the upper wall 605, and the insulating layer is further provided on the electrode 621.
The vertex portions of the upper wall 605 and the lower wall 607 are adhesively attached to one another to form the ink channels 613 and the spaces 615. Subsequently, the nozzle plate 617 having the nozzles 618 formed therein is adhesively attached to one end of the ink channels 613 and the spaces 615 so that the nozzles 618 face the ink channels 613. The other end of the ink channels 613 and the spaces 615 are connected to the silicon chip 625 and the ground 623.
A voltage is applied to the electrodes 619 and 621 of each ink channel 613 from the silicon chip 625, whereby each actuator wall 603 suffers a piezoelectric shear mode deflection in such a direction that the voluble of each ink channel 613 increases. The voltage application is stopped after a predetermined time elapses, and the volume of each ink channel 613 is restored from a volume-increased state to a natural state, so that the ink in the ink channels 613 is pressurized and ink droplets are ejected from the nozzles 618.
In the ink-ejecting device 600 as described above, the electrodes 619 and 621 that face the spaces (air channels) 615 are connected to the ground 623, and the electrodes 619 and 621 that are provided in the ink channels 613 are connected to silicon chip 625, which serves as an actuator driving circuit.
U.S. Pat. No. 4,879,568 fails to disclose a scheme or method for the above-described electrical connection. Therefore, for example, assuming the number of ink channels 613 to be fifty, fifty-one air channels 615 are required, and the electrical connection of the electrodes 619 and 621 must be performed at 101 connection positions. The connection positions are disposed at a narrow pitch, and thus it is difficult to form the connections and a long time is required to form the connections so that mass production is low.